How come? In my hometown in Spain the average low in winter is below 0º degrees celsius, which is colder than London. Even the average low in winter in Madrid is no higher than in London.
Maybe you haven't spent a winter in Spain or just in the south, but it's a common misconception. My colleagues in London won't believe me when I say winters are colder in my hometown, with frequent snowfalls. They go to Madrid or Barcelona or Majorca in summer when it's like 35ºC and they think it's the same all the year. But it's not like Spain is in the tropics. :)
Edited by MickeyPunch - 10/12/15 at 3:08am